Feature request: Print coub info to JSON

[HelpSeeker]

A feature request that reached me outside of GitHub.

Currently it's only possible to save additional information about a coub by using a custom name template and including the wanted information in the filename. The problem with this approach is that too long filenames (easily achievable with %tags%) will fall back to %id%, thus losing all additional information.

The solution is to allow the user to dump the info into a JSON file as well (similar to youtube-dl's --print-json, just with much less information).